The present invention relates generally to a reciprocating piston compressor assembly and, more particularly, to an improved suction valve retainer in a piston and valve assembly for such a compressor assembly.
In a typical reciprocating piston compressor, a cylinder is defined by a compressor crankcase and a piston reciprocates within the cylinder to compress gaseous refrigerant therein. In a compressor to which the present invention generally pertains, the piston comprises a piston valve assembly wherein a suction valve is operably mounted to the piston head to receive gaseous refrigerant through the piston from one end of the cylinder, whereupon the gas is compressed in the cylinder and thereafter discharged. A valve plate may be mounted to the crankcase so as to close the top of the cylinder. The valve plate includes a discharge valve assembly operable to discharge gas into a discharge space defined by a cylinder head cover mounted to the crankcase with the valve plate disposed therebetween.
A scotch yoke compressor includes a suction cavity defined within the crankcase into which a plurality of radially disposed cylinders open. A crankshaft is journalled in the crankcase and includes an eccentric portion located in the suction cavity to which the pistons and cylinders are operably coupled by means of a scotch yoke mechanism. In a typical scotch yoke coupling mechanism, where four radially disposed pistons are attached to a pair of U-shaped yokes, the piston bodies are attached to the yokes by means of threaded bolts, rivets, and the like. In addition, separate means are provided for retaining the suction valve component to the piston head. Such valve attachment means may comprise bolts, rivets, bosses, and the like. The provision of separate means for attaching the piston member to the scotch yoke and for attaching suction valving to the piston head requires a plurality of parts and entails a higher degree of difficulty during compressor assembly.
In a compressor assembly having a piston valve assembly, as herein described, the suction valve is mounted generally adjacent the top surface of the piston head and is reciprocatingly displaceable from a closed position adjacent the piston head to an open position a fixed distance from the piston head. A valve retainer is axially spaced a fixed distance from the piston head, to limit the displacement of the suction valve. In one prior art compressor, the suction valve is reciprocatingly displaced approximately 0.060 inch from the top of the piston head to the valve retainer. As the valve strikes the retainer, a relatively large amount of stress is placed on the retainer and valve. In order to avoid damage to this retainer, it has been necessary in prior art systems to provide a retainer having sufficient strength to resist this stress. Such retainers have generally been formed from a material having sufficient strength to withstand the stresses, or from a material having sufficient thickness such that the effect of the stress on the retainer would be minimized.
While prior art valve retainers are generally effective in limiting the valve displacement, the life of the retainer and valve may nevertheless be adversely affected as a result of an accumulation of stress cycles on the retainer and valve caused by the repeated impact of the two parts. This accumulation of stress cycles may cause a breakdown of the retainer and valve, resulting in the loss of use of the compressor assembly. Therefore, it is desired to provide a valve retainer having an improved capability for withstanding these stresses and reducing stress on the suction valve, and accordingly, having a longer life than prior art retainers and valves.
A particular prior art retainer of the type shown in U.S. Pat. No. 4,834,632 included a valve retainer approximately 0.060 inches thick and made of spring steel. Although this retainer had some flexibility, it was still not satisfactory, especially for large capacity compressors.